Calcium/sodium exchange in purified secretory vesicles from bovine neurohypophyses

Særmark, T.; Thorn, Niels A.; Gratzl, Manfred

doi:10.1016/0143-4160(83)90031-3

Cited by 42 publications

(20 citation statements)

References 31 publications

(35 reference statements)

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“…Similar observations have been made in neurohypophysial secretory vesicles (20,24). However, the colocation of cell membrane components within chromaffin vesicles in conjunction with cotransport studies on the intact tissue as well as on chromaffin cells in culture suggest a participation of chromaffin secretory vesicles in the biogenesis of the cell membrane.…”

Section: Fractionsupporting

confidence: 50%

“…The main contaminants of cmde secretory vesicle fractions (Le., those obtained by differential centrifugation) are mitochondria, which can be completely removed using such gradients. The vesicles obtained are stable and have successfully been used in studies concerned with the analysis of proton, sotium, and calcium transport (6,7,13,20,(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24).…”

Section: Resul Ts and Discussionmentioning

confidence: 99%

“…Reports from severallaboratories have indicated that lysosomal enzyme activities are found also in secretory vesicle fractions after further purification on Percoll gradients (6,20,24).…”

Section: Resul Ts and Discussionmentioning

confidence: 99%

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Distribution of chromaffin secretory vesicles, acetylcholinesterase, and lysosomal enzymes in sucrose and percoll gradients

Gratzl

1984

Analytical Biochemistry

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emde chromaffin secretory vesicles, obtained by differential centrifugation, were further purified on isotonic (PereolI) gradients. The chromaffin vesicIe fractions recovered from the gradients contain acetylcholinesterase as well as lysosomal enzymes. With the aid of a subsequent sucrose gradient lysosomal enzymes could be removed from chromaffin vesicIe fractions. but not acetylcholinesterase. This suggests that lysosomal enzymes do not pass through the chromaffin vesicIes during the biogenesis of lysosomes but acetylcholinesterase does.

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Section: Fractionsupporting

confidence: 50%

Section: Resul Ts and Discussionmentioning

confidence: 99%

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Distribution of chromaffin secretory vesicles, acetylcholinesterase, and lysosomal enzymes in sucrose and percoll gradients

Gratzl

1984

Analytical Biochemistry

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“…We cannot completely exclude the possibility that this change was caused by a partial loss of the secretory content, but it is more likely that a simple swelling of the vesicular matrix decreased the density of S atoms within the analyzed internal volume of the vesicles. It has been shown in a study of Na ϩ ͞Ca 2ϩ exchange in isolated bovine neurosecretory vesicles that swelling (monitored by optical density) could be promoted by an excess of Na taken up relative to Ca released (27). If sodium ions exchange for calcium, they will not only double the osmotic activity, thereby tending to induce water intake, but they are also likely to displace charges; it has been proposed that swelling is governed by the fixed charges of the polyionic matrix rather than by osmotic processes (28).…”

Section: Discussionmentioning

confidence: 99%

Stimulus–secretion coupling in neurohypophysial nerve endings: A role for intravesicular sodium?

Thirion

Jd²,

Nb³

et al. 1999

Proc. Natl. Acad. Sci. U.S.A.

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It is generally accepted that Ca is essentially involved in regulated secretion, but the role of this cation, as well as others such as Na, is not well understood. An illustrative example occurs in neurohypophysial secretion, where an experimentally induced increase in the cytosolic concentration of Na ؉ can induce continuous neuropeptide release. In contrast, an increase in cytosolic Ca 2؉ will have only a transient stimulatory effect. The secretion-promoting targets for Ca 2؉ are not known; they may be cytosolic, as is usually assumed, but they may also be intravesicular, especially in view of evidence that Ca-rich secretory vesicles are preferentially secreted. In the present work, we have investigated the movements of these cations into and out of secretory vesicles during stimulus-secretion coupling. Isolated rat neurohypophysial nerve endings were stimulated by potassium (55 mM) depolarization, and at 6 min (peak secretion) and 20 min after the onset of stimulation, the elemental content of individual secretory vesicles was measured by quantitative x-ray microanalysis. A depolarization-induced transient increase in intravesicular Na ؉ concentration was found to coincide with the onset of secretion. Moreover, only a predicted small fraction of peripheral vesicles-presumably the docked ones-were Na ؉ -loaded. The low sulfur concentration of Na ؉ -rich vesicles most likely resulted from vesicle swelling. The results suggest that high intravesicular Na ؉ concentrations in docked vesicles, occurring by Na ؉ ͞Ca 2؉ exchange or by transient fusion pore opening, is a proximal event in exocytosis. Ca 2ϩplays an essential role in several stimulatory, and perhaps also inhibitory, steps of regulated exocytosis but, despite much recent progress, its precise targets are still largely a matter of debate (1-3). In neurohypophysial secretion particularly, it is clear that Ca 2ϩ cannot be the ultimate and sufficient trigger for neurosecretion, because the obligatory depolarizationinduced increase in cytosolic Ca 2ϩ concentration stimulates release for only a few minutes (4, 5), even when depolarization is maintained. This behavior contrasts with the known but mechanistically obscure secretagogue effect of Na ϩ (6-8), wherein an artificially induced increase in cytosolic Na ϩ concentration can induce a sustained and continuous secretion (8). In previous work on neurohypophysial nerve endings, one of our laboratories reported that the Ca content of the secretory vesicles increased upon secretory stimulation, and that Ca-rich vesicles accumulated when secretion was blocked (9), suggesting a role of intravesicular ion concentration in the secretory mechanism. This hypothesis is further supported by observation that in insulin-secreting cells, Ca 2ϩ depletion from secretory granules inhibits exocytosis (10). Because the swelling of some granule matrices is inhibited by Ca 2ϩ and promoted by Na ϩ (11, 12), we have investigated in isolated and stimulated rat neurohypophysial nerve endings possible changes in the concentra...

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“…Ca2+ from neurosecretory granules (Saermark, Thorn & Gratzl, 1983), Ca2+ release from microvesicles is relatively insensitive to internal concentrations of Na+ (Nordmann & Chevalier, 1980).…”

Section: Na+-dependent Secretionmentioning

confidence: 99%

Effect of sodium and calcium on basal secretory activity of rat neurohypophysial peptidergic nerve terminals.

Toescu¹,

Nordmann²

1991

The Journal of Physiology

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SUMMARY1. The release of arginine vasopressin (AVP) from a perifused preparation of peptidergic nerve terminals isolated from rat neurohypophyses was studied during manipulations of the external sodium and calcium concentrations. Intracellular concentrations of these two ions were manipulated by use of ouabain and a calcium ionophore, respectively.2. Removal of extracellular Na+ caused, in a concentration-dependent manner, a significant decrease of secretory activity. Conversely, graded addition of Na+ to a Na+-free perifusion medium increased secretion. Half-maximal activation of secretory activity was attained at ca 75 mm [Na+]O. 5. Ouabain (0O1 mM) increased the basal secretory activity and potentiated the secretory response to removal of Ca2+ from the perifusion medium.6. The Ca2+ ionophore A23187 stimulated, in a concentration-dependent fashion, the secretory activity of the peptidergic nerve terminals and this stimulation was strictly dependent on the presence of Ca2+ in the perifusion medium.7. These results show that basal secretion is directly dependent on [Na+]o and indicate that intracellular Na+ is an important factor in the control of secretory mechanisms. Evidence is presented in regard to a possible antagonistic effect of extracellular Ca2+ and Na+ on secretion.

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Calcium/sodium exchange in purified secretory vesicles from bovine neurohypophyses

Cited by 42 publications

References 31 publications

Distribution of chromaffin secretory vesicles, acetylcholinesterase, and lysosomal enzymes in sucrose and percoll gradients

Distribution of chromaffin secretory vesicles, acetylcholinesterase, and lysosomal enzymes in sucrose and percoll gradients

Stimulus–secretion coupling in neurohypophysial nerve endings: A role for intravesicular sodium?

Effect of sodium and calcium on basal secretory activity of rat neurohypophysial peptidergic nerve terminals.

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